Compositions and methods of treating retinal disease

ABSTRACT

Compositions and methods for treating macular degeneration and other forms of retinal disease whose etiology involves the accumulation of A2E and/or lipofuscin, and, more specifically, for preventing the formation and/or accumulation of A2E are disclosed

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/861,332, filed Jan. 3, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/488,205, filed Apr. 14, 2017, issued as U.S.Pat. No. 9,896,419, which is a continuation of U.S. patent applicationSer. No. 15/049,890, filed Feb. 22, 2016, issued as U.S. Pat. No.9,650,342, which is a continuation of U.S. patent application Ser. No.14/581,462, filed Dec. 23, 2014, issued as U.S. Pat. No. 9,265,759,which is a continuation of U.S. patent application Ser. No. 13/175,218,filed Jul. 1, 2011, issued as U.S. Pat. No. 8,940,721, which is acontinuation of U.S. patent application Ser. No. 11/441,848, filed May26, 2006, issued as U.S. Pat. No. 7,973,025, which claims the benefit ofU.S. Provisional Application No. 60/685,460, filed May 26, 2005 and U.S.Provisional Application No. 60/723,577, filed Oct. 4, 2005. The entirecontents of each cited priority application are incorporated byreference herein.

FIELD OF THE INVENTION

This application relates to compositions and methods for treatingmacular degeneration and other forms of retinal disease whose etiologyinvolves the accumulation of A2E and/or lipofuscin in retinal tissue,more specifically, for preventing the accumulation of A2E.

BACKGROUND OF THE INVENTION

Two forms of retinal disease include Stargardt disease, which afflictsyoung adults, and age related macular degeneration (AMD), which afflictsadults in midlife and later. Both forms are characterized by theprogressive degeneration of cone photoreceptors located in the fovealregion of the macula, which degeneration leads to loss of high acuityvision in the central visual field. The disease has been associated withthe accumulation of toxic biochemicals, including lipofuscin, insideretinal pigment epithelium (RPE) cells and extracellular drusen wherethe RPE cells are in contact with Bruch's membrane. The accumulation ofthese retinotoxic mixtures is one of the most important known riskfactors in the etiology of AMD.

AMD begins as a “dry form” without vascular complications. Currentlythere are no known treatments for dry form AMD. One patient in tenprogresses to a late-stage form of the disease known as “wet form” AMDwhich is characterized by choroidal neovascularization that invades themacula and disrupts retinal and RPE tissue. Most current wet form AMDtreatments suppress vascular growth or inflammatory processes.

During the normal visual cycle (summarized in FIG. 1), most trans-RAL issequestered by opsin proteins in photoreceptor outer segment discmembranes. This sequestering mechanism protects the trans-RAL group fromreacting with phosphatidylethanolamine (PE) before trans-RALdehydrogenase (RDH) converts trans-RAL to the alcohol trans-retinol.Some trans-RAL molecules escape sequestering, however, and react withphosphatidylethanolamine to form firstN-retinylidene-phosphatidylethanolamine (APE) and thenN-retinylidene-N-retinyl-phosphatidylethanolamine (A2PE) in the discs ofphotoreceptor outer segments. Both A2PE and trans-RAL that has escapedsequestering are transported out of photoreceptor disc membranes by anATP-binding cassette transporter called Rim protein (RmP) or ABCA4(formerly ABCR). Following this transportation, trans-RAL is reduced totrans-retinol by RDH and crosses the outer-segment (OS) plasma membraneinto the extracellular space where it is taken up by cells of theretinal pigment epithelium (RPE).

A2PE is taken up by RPE cell lysosomes when RPE cells ingestphotoreceptor outer segments that are shed routinely. Once inside thelysosomes, A2PE is converted irreversibly to A2E, which causes lysosomalfailure. Lysosomal failure poisons the RPE cells and compromises theirability to provide biochemical support to retinal photoreceptors,leading to the progressive degeneration of both cell types.

Multiple factors affect the rate of A2E accumulation, both genetic andenvironmental. For example, a hereditary mutation in both copies of theABCA4 transporter gene increases the accumulation of A2E and leads toStargardt disease in children and young adults. A later onset form ofStargardt disease is associated with ABCA4 mutations that are morebenign. Stargardt disease is thought by many to be an early onset formof AMD, where the normal age-related accumulation of A2E is acceleratedby the ABCA4 mutation to a sufficient extent that the disease istriggered decades before AMD normally appears.

With respect to environmental factors, it is well established in animalmodels that the rate of A2E formation varies with light exposure. It hasbeen shown that a fatty acid (phosphatidylglycerol) can protect RPEcells from A2E induced cell death, and that other dietary factors caninfluence disease progression, including zinc (which affects retinoloxidoreductase activity).

There is a need for effective treatments of dry form AMD and Stargardtdisease which arrest disease progression and preserve or restore vision.

SUMMARY OF THE INVENTION

The invention relates to compositions and methods for treating maculardegeneration and other forms of retinal disease whose etiology involvesthe accumulation of A2E and/or lipofuscin in retinal tissue.

In one embodiment, the present invention provides compositions andmethods for treating macular degeneration and other retinal disease withan etiology involving the accumulation of A2E and/or lipofuscin bylimiting the formation of cytotoxic A2E. For example, A2E formation isprevented or reduced by limiting the amount of unsequestered trans-RALavailable for reaction with phosphatidyl ethanolamine (PE) inphotoreceptor outer segments. In one approach, a therapeutic compound,i.e., an “RAL-trap” is administered to a patient, whereby the drugcompetes with PE for trans-RAL by forming a Schiff base adduct. “FreeRAL” is defined as RAL that is not bound to a visual cycle protein.

In another embodiment, the invention relates to a method of identifyinga drug to treat macular degeneration and other forms of retinal diseasewhose etiology involves the accumulation of A2E and/or lipofuscin mayinclude administering a candidate agent to a subject having, or at riskfor developing, macular degeneration and retinal disease, and measuringA2E formation in the presence of the candidate agent, relative to A2Eformation in the absence of the candidate agent.

A wide variety of drugs are contemplated for use in the methods of theinvention. In some embodiments, inhibitors of A2E formation includeRAL-traps. For example, the pharmacological target of such RAL-trapcompounds is trans-RAL which has escaped sequestering by opsins inphotoreceptor outer segments. RAL-traps include, for example, cyclicamines and five- and six-membered heterocyclic amines which may have oneor more pairs of conjugated double bonds, and, for example, may bearomatic. In some embodiments, the RAL trap is administered to a subjectas a topical formulation for delivery by eye drops or via skin patch.

The invention relates to a method of treating or preventing maculardegeneration and other forms of retinal disease whose etiology involvesthe accumulation of A2E and/or lipofuscin in a subject, the method byadministering a composition that reduces the level of A2E accumulationrelative to the level of A2E accumulation in the subject withoutadministration of the composition. The invention also relates to amethod of treating or preventing macular degeneration and other forms ofretinal disease whose etiology involves the accumulation of A2E and/orlipofuscin in a subject by administering to the subject a compositionthat reduces the level of A2E formation relative to the level of A2Eformation in the subject without administration of the composition.

In some embodiments, the methods of the invention further includediagnosing macular degeneration and other forms of retinal disease whoseetiology involves the accumulation of A2E and/or lipofuscin in thesubject. In other embodiments, the methods further include monitoringthe macular degeneration and other forms of retinal disease whoseetiology involves the accumulation of A2E and/or lipofuscin in thesubject.

In one aspect, the invention relates to administering a composition thatincludes a compound selected from benzocaine, procaine, orthocaine,tricaine (MS222, compound 6), and methyl anthranilate.

In one aspect, the methods of the invention include administering acomposition that includes a compound of the formula IV:

where X is O, N(H), or S, het is a 5 or 6-membered heterocycle, n is 0,1, 2, or 3, and each D is an unbranched lower alkyl group. Each D can bethe same or different. In one embodiment, the D_(S) are the same.

U is a substituent selected from halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms.

In one embodiment each D is methyl.

In some embodiments, the substituents (U) are selected such that thefirst pK_(a) of the ring NH₂ is approximately 3.5.

In one aspect, the methods of the invention include administering acomposition that includes a compound of formula I:

where, W, X, Y, and Z are each, independently, N, S, O, CU or CH, and atleast one of W, X, Y, and Z is N; n is 0, 1, 2, 3, or 4, A is

D is unbranched lower alkyl; R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7, or C8, straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8, branched chain alkyl.

U is a substituent selected from a halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms.

In one embodiment, the identity of W, X, Y, and Z are such that thecompound comprises a pyridine, pyridazine, pyrazine, or pyrimidine ring.

In some embodiments, U is aryl. For example, U can be benzene. U canalso be a halo-substituted benzene.

In some embodiments, A is

In some embodiments, A is

and D is methyl.

In some embodiments, two adjacent U substituents are connected to form a5- or 6-membered optionally substituted ring. For example, thesubstituents can be connected to form a benzene ring, forming a compoundhaving the structure according to formula Ia:

where X, Y, and Z are each, independently, N, O, S, CH, or absent, suchthat at least one of X, Y, and Z is N; p is 0, 1, 2, or 3, B is ahalogen atom, hydroxyl, carbamoyl, substituted or unsubstituted aryl oramino, A is

D is unbranched lower alkyl, and R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl.

Compounds of Formula 1 can include:

In one embodiment, the composition used in the methods of the inventionincludes the compound

or a pharmaceutically acceptable salt thereof.

In one aspect, the methods of the invention include administering acomposition that includes a compound of formula II or IIa:

where Q, T, and V are each, independently, N or NH, S, O, CU or CH, suchthat at least one of Q, T and V is not CU or CH; the dashed ringrepresents two double bonds within the ring, which comply with thevalency requirements of the atoms and heteroatoms present in the ring mis 0, 1, or 2; A is

D is unbranched lower alkyl; R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7 or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl.

U is a substituent selected from a halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms.

In one embodiment, in compounds of formula II or IIa, U is aryl. Forexample, U can be benzene. U can also be a halo-substituted benzenering.

In some embodiments, in compounds of formula II or IIa, A is

In some compounds, each D is methyl.

In one embodiment, in compounds of formula II or IIa, Q, T, and V areselected such that the composition includes a furan or thiophene ring.

In one embodiment, in compounds of formula II or IIa, U is lower alkyl.For example, U can be methyl.

In one embodiment, in compounds of formula II or IIa, U is a halogenatom. For example, U can be fluoro or chloro.

One example of a composition useful in the methods of the inventionincludes the compound

or a pharmaceutically acceptable salt thereof.

In one aspect, the methods of the invention include administering acomposition that includes a compound of formula III:

where, L is a bond or CH₂; A is

D is unbranched lower alkyl; R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7 or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl, and k is 0,1, 2, 3, or 4.

U is a substituent selected from a halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms.

In some embodiments, in compounds of formula III, A is

In some compounds, each D is methyl.

In some embodiments, in compounds of formula III, U is aryl. Forexample, U can be benzene. In some embodiments, U is a halo-substitutedbenzene ring.

In one aspect, the methods of the invention include administering acomposition that includes a compound of formula III, wherein twoadjacent U substituents are connected to form a 5- or 6-membered,optionally substituted ring.

For example, methods of the invention include administering acomposition that includes a compound of formula III, where adjacent Usubstituents are connected as a heterocyclic ring, forming a compoundhaving the structure according to formula IIIa:

IIIa

wherein L is a single bond or CH₂,X, Y, and Z are each, independently, N, NH, O, S, CB, CH, or absent,such that at least one of X, Y, and Z is N or NH; p is 0, 1, 2, or 3; Bis a halogen atom, hydroxyl, carbamoyl, aryl or amino;A is

D is unbranched lower alkyl; and R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl.

In one embodiment, in the compound of formula IIIa, the fusedheterocyclic ring is a 6-membered ring. For example, the ring can be apyridine ring.

In one embodiment, in the compound of formula IIIa, the fusedheterocyclic ring is a 5-membered ring. For example, the ring can bethiazole, oxazole, or imidazole.

In one embodiment, in the compound of formula IIIa, B is aryl. Forexample, B is benzene.

In one embodiment, methods of the invention include administering acomposition that includes a compound selected from

or pharmaceutically acceptable salts thereof.

In one aspect, methods of the invention include administering acomposition chronically to treat or prevent macular degeneration andother forms of retinal disease whose etiology involves the accumulationof A2E and/or lipofuscin.

In one aspect, the invention also relates to a method of identifying adrug for treating or preventing macular degeneration and other forms ofretinal disease whose etiology involves the accumulation of A2E and/orlipofuscin, by administering a candidate drug to a subject having, orwho is at risk for developing, macular degeneration or other forms ofretinal disease whose etiology involves the accumulation of A2E and/orlipofuscin; and measuring accumulation of A2E in the subject; wherereduced accumulation of A2E in the presence of the candidate drugrelative to accumulation of A2E in the absence of the candidate drugindicates that the candidate drug is a drug for treating or preventingmacular degeneration and other forms of retinal disease whose etiologyinvolves the accumulation of A2E and/or lipofuscin.

In another aspect, the invention relates to a method of identifying adrug for treating or preventing macular degeneration and other forms ofretinal disease whose etiology involves the accumulation of A2E and/orlipofuscin, by: contacting an in-vitro model of the visual cycle withthe candidate drug; and measuring accumulation of A2E; wherein reducedaccumulation of A2E in the presence of the candidate drug relative toaccumulation of A2E in the absence of the candidate drug indicates thatthe candidate drug is a drug for treating or preventing maculardegeneration and other forms of retinal disease whose etiology involvesthe accumulation of A2E and/or lipofuscin.

The present invention relates to compounds and their use to treatmacular degeneration, including dry form AMD and Stargardt disease, andother forms of retinal disease whose etiology involves the accumulationof A2E and/or lipofuscin. One aspect of the invention includes acompound of formula I, Ia, II, IIa, III, IIIa, or IV wherein a SchiffBase adduct of said compound and 11-cis-RAL possesses an extinctioncoefficient equal to or less than that of free 11-cis-RAL. In oneembodiment, the absorbance peak of the Schiff Base adduct is at awavelength equal to or lower than that of free 11-cis-RAL.

Another aspect of the invention includes a compound having the formulaIV:

wherein X is O, N(H), or S and het is a 5 or 6-membered heterocycle. nrepresents 0, 1, 2, or 3, and each D is an unbranched lower alkyl group.U is a substituent selected from halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms. Inanother embodiment, each D is methyl. In another embodiment, the pK_(a)of the ring NH₂ (NH₂→NH) is approximately 3.5.

Another aspect of the invention includes a compound represented bygeneral formula I:

W, X, Y, and Z are each, independently, N, S, O, CU or CH, such that atleast one of W, X, Y, and Z is N. A is

D is unbranched lower alkyl. R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7, or C8, straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8, branched chain alkyl. U is asubstituent selected from a halogen atom; cyano; lower alkyl wherein oneor more hydrogen atoms on the lower alkyl group are optionallysubstituted by groups selected from a halogen atom, hydroxyl, carbamoyl,amino, aryl, and a monocyclic or bicyclic heterocyclic group containingone or more hetero-atoms selected from nitrogen, oxygen, and sulfuratoms; lower alkylthio wherein one or more hydrogen atoms on the alkylgroup are optionally substituted by groups selected from a halogen atom,hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl wherein one ormore hydrogen atoms on the alkyl group are optionally substituted bygroups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms. nrepresents 0, 1, 2, 3, or 4. In one embodiment, the compound comprises apyridine, pyridazine, pyrazine, or pyrimidine ring. In anotherembodiment, U is an aryl. In another embodiment, U is a benzene. Inanother embodiment, U is a halo-substituted benzene. In one embodiment,A is

and D is methyl. In another embodiment, two adjacent U substituents areconnected to form a 5- or 6-membered optionally substituted ring. Inanother embodiment, two adjacent U substituents are connected as abenzene ring, forming a compound having the structure according toformula Ia:

X, Y, and Z are each, independently, N, O, S, C(H), or absent, such thatat least one of X, Y, and Z is N. p is 0, 1, 2, or 3. B is a halogenatom, hydroxyl, carbamoyl, aryl or amino. A is

D is unbranched lower alkyl, and R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8 branched chain alkyl.

In one embodiment, the composition comprises a compound selected from:

In a further embodiment, the compound is selected from

and pharmaceutically acceptable salts thereof.

Another aspect of the invention includes a compound represented byformula II or IIa:

Q, T, and V are each, independently. N(H), S, O, CU or CH, such that atleast one of Q, T and V is not CU or CH. The dashed ring represents twodouble bonds within the ring, which comply with the valency requirementsof the atoms and heteroatoms present in the ring. m is 0, 1, or 2. A is

D is unbranched lower alkyl. R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7 or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8 branched chain alkyl. U is asubstituent selected from a halogen atom; cyano; lower alkyl wherein oneor more hydrogen atoms on the lower alkyl group are optionallysubstituted by groups selected from a halogen atom, hydroxyl, carbamoyl,amino, aryl, and a monocyclic or bicyclic heterocyclic group containingone or more hetero-atoms selected from nitrogen, oxygen, and sulfuratoms; lower alkylthio wherein one or more hydrogen atoms on the alkylgroup are optionally substituted by groups selected from a halogen atom,hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl wherein one ormore hydrogen atoms on the alkyl group are optionally substituted bygroups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms. In oneembodiment, U is an aryl. In another embodiment, U is a benzene. Inanother embodiment, U is a halo-substituted benzene. In one embodiment,A is

In another embodiment, each D is methyl. In another embodiment, Q, T,and V are selected such that the composition comprises a furan orthiophene ring. In another embodiment, U is lower alkyl. In anotherembodiment, U is methyl. In another embodiment, U is halogen atom. Inanother embodiment, U is fluoro. In a further embodiment, the compoundis selected from

and pharmaceutically acceptable salts thereof.

Another aspect of the invention includes a compound represented bygeneral formula III

L is a single bond or CH₂. A is

D is unbranched lower alkyl. R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8 branched chain alkyl. U is asubstituent selected from a halogen atom; cyano; lower alkyl wherein oneor more hydrogen atoms on the lower alkyl group are optionallysubstituted by groups selected from a halogen atom, hydroxyl, carbamoyl,amino, aryl, and a monocyclic or bicyclic heterocyclic group containingone or more hetero-atoms selected from nitrogen, oxygen, and sulfuratoms; lower alkylthio wherein one or more hydrogen atoms on the alkylgroup are optionally substituted by groups selected from a halogen atom,hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl wherein one ormore hydrogen atoms on the alkyl group are optionally substituted bygroups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms. k is 0,1, 2, 3, or 4. In one embodiment, A is

In another embodiment, each D is methyl. In another embodiment, U is anaryl. In another embodiment, U is a benzene. In another embodiment, U isa halo-substituted benzene. In another embodiment, two adjacent Usubstituents are connected to form a 5- or 6-membered optionallysubstituted ring. In another embodiment, two adjacent U substituents areconnected as a heterocyclic ring, forming a compound having thestructure according to formula IIIa:

X, Y, and Z are each, independently, N, O, S, CB, CH, or absent, suchthat at least one of X, Y, and Z is N. p is 0, 1, 2, or 3. B is ahalogen atom, hydroxyl, carbamoyl, aryl or amino. A is

D is unbranched lower alkyl. R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8 branched chain alkyl. In oneembodiment, the fused heterocyclic ring is a 6-membered ring. In anotherembodiment, the fused heterocyclic ring is a pyridine ring. In anotherembodiment, the fused heterocyclic ring is a 5-membered ring. In anotherembodiment, the fused heterocyclic ring is selected from thiazole,oxazole, and imidazole. In another embodiment, B is aryl. In anotherembodiment, B is a benzene. In another embodiment, the compound isselected from

and pharmaceutically acceptable salts thereof.

Pharmaceutical compositions that include a compound of Formula I, Ia,II, IIa, III, IIIa, or IV or a pharmaceutically acceptable salt thereofare used in the methods of the invention. In one embodiment, thecompound of Formula I, Ia, II, IIa, III, IIIa, or IV or apharmaceutically acceptable salt thereof is co-administered with one ormore additional therapies.

The above description sets forth rather broadly the more importantfeatures of the present invention in order that the detailed descriptionthereof that follows may be understood, and in order that the presentcontributions to the art may be better appreciated. Other objects andfeatures of the present invention will become apparent from thefollowing detailed description considered in conjunction with theexamples.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of the visual cycle.

FIG. 2 is a schematic of the reaction pathway of A2E formation.

FIG. 3 is a schematic of Schiff base formation.

FIG. 4a is a UV-vis spectrum of compound 6 and RAL; FIG. 4b is a graphof the formation of the Schiff base adduct.

FIG. 5 is a graph of standard curve for ERG measurement of retinalresponses to experimental stimuli of varying light intensity.

FIG. 6a is a graph of ERG measurement of the dark adaptation rate of aphoto-bleached rat during anesthesia, and FIG. 6b is a graph of EGRmeasurement of the dark adaptation of a photo-bleached rat withoutanesthesia.

FIG. 7 is a graph of the effect of compound 6 on ERG light sensitivityof a dark-adapted rat.

FIG. 8 is a graph showing RAL-compound 8 reaction kinetics by NMR.

DETAILED DESCRIPTION OF THE INVENTION

The present application provides compositions and methods for treatingmacular degeneration and other forms of retinal disease whose etiologyinvolves the accumulation of A2E and/or lipofuscin, for example, bylimiting the formation of cytotoxic A2E. A2E formation can be preventedor reduced by limiting the amount of trans RAL available for reactionwith phosphatidyl ethanolamine (PE). Progressive A2E accumulation in RPEcells causes dry AMD. By reducing the amount of A2E accumulation, thepresent invention prevents the onset and/or progression of dry AMD. Inone approach, a small molecule drug is administered that competes withPE for reaction with trans-RAL which has escaped sequestering by opsinsin photoreceptor outer segments.

As shown in FIG. 2, RAL contains an aldehyde group. The aldehyde groupstabilizes the binding of 11-cis-RAL to a photoreceptor membrane proteincalled opsin, by forming a Schiff base (FIG. 3) with an amino acidsidechain in the opsin binding site. Opsin releases trans-RAL from thisbinding site after transducing the photo-isomerization of bound11-cis-RAL through a second messenger pathway.

While the aldehyde group on RAL is a useful molecular anchor for opsinbinding, it is otherwise hazardous because of its Schiff base reactivitywith other biological amines. To mitigate this risk, visual cycleproteins have evolved molecular mechanisms to continuously sequester RALmolecules, and thereby shield the aldehyde group from chemical sidereactions. However, these protein sequestering mechanisms are notcompletely reliable. Over time, as much as one trans-RAL molecule inthree escapes protein sequestering, where it is free to initiate areaction cascade which begins with the formation of A2PE inphotoreceptor outer segments and culminates in the formation of A2E inRPE cell lysosymes.

Once it is formed inside RPE cell lysosomes, A2E inhibits the ATP-drivenproton pump in lysosome membranes and causes lysosomal pH to increase.The pH increase deactivates acid hydrolases and thereby causes lysosomalfailure. Lysosomal failure is also caused the detergent action of A2E,which solubilizes lysosomal membranes. Lysosomal failure poisons the RPEcells and compromises their ability to provide biochemical support toretinal photoreceptors, leading to the progressive degeneration of bothcell types and visual deterioration.

Hydroxyl amine and aromatic amine compounds were described as aldehydenucleophiles in Schiff base reactions with RAL by Hubbard in 1956.Hubbard, J. Am. Chem. Soc. 78:4662, 1956; see also Rapp and Basinger,Vision Res. 22:1097, 1982, and Fowler et al., J. Photochem. Photobiol. B8:183, 1991. Two such compounds which have a history of safe human usefor other purposes include methyl anthranilate, a natural product foundin grapes, and MS-222, a fish anesthetic used by fish breeders who areexposed to it occupationally during fish handling. However, MS-222 ispharmacologically active in the human retina and has no anestheticactivity in mammals.

In 1963, Dowling showed that anesthetics slow rhodopsin regeneration anddark adaptation in rats. This was the first report that such smallmolecules could modulate retinal visual performance. Dowling, J. Gen.Physiol. 46:1287, 1963. In 1982, Rapp & Basinger showed that certainlocal anesthetics form Schiff bases with RAL and slow dark adaptation infrogs. This was the first elucidation of the chemical reaction mechanismby which these compounds modulate retinal visual performance. Rapp andBasinger, Vision Res. 22:1097, 1982. In 1997, Bernstein et al. showedthat MS222 (6) attenuates night vision reversibly in human occupationalexposure. This was the first report that one such compound can beabsorbed by the skin and modulate human retinal vision reversibly withno known side effects. Bernstein et al., Am. J. Opthalmol. 124:843,1997.

Definitions

For convenience, before further description of exemplary embodiments,certain terms employed in the specification, examples, and appendedclaims are collected here.

These definitions should be read in light of the remainder of thedisclosure and as understood by a person of skill in the art.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

The terms “comprise,” “comprising,” “include,” “including,” “have,” and“having” are used in the inclusive, open sense, meaning that additionalelements may be included. The terms “such as”, “e.g.”, as used hereinare non-limiting and are for illustrative purposes only. “Including” and“including but not limited to” are used interchangeably.

The term “or” as used herein should be understood to mean “and/or”,unless the context clearly indicates otherwise.

In the present specification, the structural formula of the compoundrepresents a certain isomer for convenience in some cases, but thepresent invention includes all isomers such as geometrical isomer,optical isomer based on an asymmetrical carbon, stereoisomer, tautomerand the like which occur structurally and an isomer mixture and is notlimited to the description of the formula for convenience, and may beany one of isomer or a mixture. Therefore, an asymmetrical carbon atommay be present in the molecule and an optically active compound and aracemic compound may be present in the present compound, but the presentinvention is not limited to them and includes any one. In addition, acrystal polymorphism may be present but is not limiting, but any crystalform may be single or a crystal form mixture, or an anhydride orhydrate. Further, so-called metabolite which is produced by degradationof the present compound in vivo is included in the scope of the presentinvention.

It will be noted that the structure of some of the compounds of theinvention include asymmetric (chiral) carbon atoms. It is to beunderstood accordingly that the isomers arising from such asymmetry areincluded within the scope of the invention, unless indicated otherwise.Such isomers can be obtained in substantially pure form by classicalseparation techniques and by stereochemically controlled synthesis. Thecompounds of this invention may exist in stereoisomeric form, thereforecan be produced as individual stereoisomers or as mixtures.

“Isomerism” means compounds that have identical molecular formulae butthat differ in the nature or the sequence of bonding of their atoms orin the arrangement of their atoms in space. Isomers that differ in thearrangement of their atoms in space are termed “stereoisomers”.Stereoisomers that are not mirror images of one another are termed“diastereoisomers”, and stereoisomers that are non-superimposable mirrorimages are termed “enantiomers”, or sometimes optical isomers. A carbonatom bonded to four nonidentical substituents is termed a “chiralcenter”.

“Chiral isomer” means a compound with at least one chiral center. It hastwo enantiomeric forms of opposite chirality and may exist either as anindividual enantiomer or as a mixture of enantiomers. A mixturecontaining equal amounts of individual enantiomeric forms of oppositechirality is termed a “racemic mixture”. A compound that has more thanone chiral center has 2^(n-1) enantiomeric pairs, where n is the numberof chiral centers. Compounds with more than one chiral center may existas either an individual diastereomer or as a mixture of diastereomers,termed a “diastereomeric mixture”. When one chiral center is present, astereoisomer may be characterized by the absolute configuration (R or S)of that chiral center. Absolute configuration refers to the arrangementin space of the substituents attached to the chiral center. Thesubstituents attached to the chiral center under consideration areranked in accordance with the Sequence Rule of Cahn, Ingold and Prelog.(Cahn et al., Angew. Chem. Inter. Edit. 1966, 5, 385; errata 511; Cahnet al., Angew. Chem. 1966, 78, 413; Cahn and Ingold, J. Chem. Soc. 1951(London), 612; Cahn et al., Experientia 1956, 12, 81; Cahn, J., Chem.Educ. 1964, 41, 116).

“Geometric Isomers” means the diastereomers that owe their existence tohindered rotation about double bonds. These configurations aredifferentiated in their names by the prefixes cis and trans, or Z and E,which indicate that the groups are on the same or opposite side of thedouble bond in the molecule according to the Cahn-Ingold-Prelog rules.

Further, the structures and other compounds discussed in thisapplication include all atropic isomers thereof. “Atropic isomers” are atype of stereoisomer in which the atoms of two isomers are arrangeddifferently in space. Atropic isomers owe their existence to arestricted rotation caused by hindrance of rotation of large groupsabout a central bond. Such atropic isomers typically exist as a mixture,however as a result of recent advances in chromatography techniques, ithas been possible to separate mixtures of two atropic isomers in selectcases.

The terms “crystal polymorphs” or “polymorphs” or “crystal forms” meanscrystal structures in which a compound (or salt or solvate thereof) cancrystallize in different crystal packing arrangements, all of which havethe same elemental composition. Different crystal forms usually havedifferent X-ray diffraction patterns, infrared spectral, melting points,density hardness, crystal shape, optical and electrical properties,stability and solubility. Recrystallization solvent, rate ofcrystallization, storage temperature, and other factors may cause onecrystal form to dominate. Crystal polymorphs of the compounds can beprepared by crystallization under different conditions.

Additionally, the compounds of the present invention, for example, thesalts of the compounds, can exist in either hydrated or unhydrated (theanhydrous) form or as solvates with other solvent molecules. Nonlimitingexamples of hydrates include monohydrates, dihydrates, etc. Nonlimitingexamples of solvates include ethanol solvates, acetone solvates, etc.

“Solvates” means solvent addition forms that contain eitherstoichiometric or non stoichiometric amounts of solvent. Some compoundshave a tendency to trap a fixed molar ratio of solvent molecules in thecrystalline solid state, thus forming a solvate. If the solvent is waterthe solvate formed is a hydrate, when the solvent is alcohol, thesolvate formed is an alcoholate. Hydrates are formed by the combinationof one or more molecules of water with one of the substances in whichthe water retains its molecular state as H₂O, such combination beingable to form one or more hydrate.

“Tautomers” refers to compounds whose structures differ markedly inarrangement of atoms, but which exist in easy and rapid equilibrium. Itis to be understood that compounds of Formula I may be depicted asdifferent tautomers. It should also be understood that when compoundshave tautomeric forms, all tautomeric forms are intended to be withinthe scope of the invention, and the naming of the compounds does notexclude any tautomer form.

Some compounds of the present invention can exist in a tautomeric formwhich are also intended to be encompassed within the scope of thepresent invention.

The compounds, salts and prodrugs of the present invention can exist inseveral tautomeric forms, including the enol and imine form, and theketo and enamine form and geometric isomers and mixtures thereof. Allsuch tautomeric forms are included within the scope of the presentinvention. Tautomers exist as mixtures of a tautomeric set in solution.In solid form, usually one tautomer predominates. Even though onetautomer may be described, the present invention includes all tautomersof the present compounds

A tautomer is one of two or more structural isomers that exist inequilibrium and are readily converted from one isomeric form to another.This reaction results in the formal migration of a hydrogen atomaccompanied by a switch of adjacent conjugated double bonds. Insolutions where tautomerization is possible, a chemical equilibrium ofthe tautomers will be reached. The exact ratio of the tautomers dependson several factors, including temperature, solvent, and pH. The conceptof tautomers that are interconvertable by tautomerizations is calledtautomerism.

Of the various types of tautomerism that are possible, two are commonlyobserved. In keto-enol tautomerism a simultaneous shift of electrons anda hydrogen atom occurs. Ring-chain tautomerism, is exhibited by glucose.It arises as a result of the aldehyde group (—CHO) in a sugar chainmolecule reacting with one of the hydroxy groups (—OH) in the samemolecule to give it a cyclic (ring-shaped) form.

Tautomerizations are catalyzed by: Base: 1. deprotonation; 2. formationof a delocalized anion (e.g., an enolate); 3. protonation at a differentposition of the anion; Acid: 1. protonation; 2. formation of adelocalized cation; 3. deprotonation at a different position adjacent tothe cation.

Common tautomeric pairs are: ketone-enol, amide-nitrile, lactam-lactim,amide-imidic acid tautomerism in heterocyclic rings (e.g., in thenucleobases guanine, thymine, and cytosine), amine-enamine andenamine-enamine. Examples include:

As used herein, the term “analog” refers to a chemical compound that isstructurally similar to another but differs slightly in composition (asin the replacement of one atom by an atom of a different element or inthe presence of a particular functional group, or the replacement of onefunctional group by another functional group). Thus, an analog is acompound that is similar or comparable in function and appearance, butnot in structure or origin to the reference compound.

As defined herein, the term “derivative”, refers to compounds that havea common core structure, and are substituted with various groups asdescribed herein. For example, all of the compounds represented byformula I are indole derivatives, and have formula I as a common core.

The term “bioisostere” refers to a compound resulting from the exchangeof an atom or of a group of atoms with another, broadly similar, atom orgroup of atoms. The objective of a bioisosteric replacement is to createa new compound with similar biological properties to the parentcompound. The bioisosteric replacement may be physicochemically ortopologically based. Examples of carboxylic acid bioisosteres includeacyl sulfonimides, tetrazoles, sulfonates, and phosphonates. See, e.g.,Patani and LaVoie, Chem. Rev. 96, 3147-3176 (1996).

The phrases “parenteral administration” and “administered parenterally”are art-recognized terms, and include modes of administration other thanenteral and topical administration, such as injections, and include,without limitation, intravenous, intramuscular, intrapleural,intravascular, intrapericardial, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intra-articular, subcapsular,subarachnoid, intraspinal and intrasternal injection and infusion.

The term “treating” is art-recognized and includes inhibiting a disease,disorder or condition in a subject, e.g., impeding its progress; andrelieving the disease, disorder or condition, e.g., causing regressionof the disease, disorder and/or condition. Treating the disease orcondition includes ameliorating at least one symptom of the particulardisease or condition, even if the underlying pathophysiology is notaffected.

The term “preventing” is art-recognized and includes stopping a disease,disorder or condition from occurring in a subject which may bepredisposed to the disease, disorder and/or condition but has not yetbeen diagnosed as having it. Preventing a condition related to a diseaseincludes stopping the condition from occurring after the disease hasbeen diagnosed but before the condition has been diagnosed.

A “pharmaceutical composition” is a formulation containing the disclosedcompounds in a form suitable for administration to a subject. In apreferred embodiment, the pharmaceutical composition is in bulk or inunit dosage form. The unit dosage form is any of a variety of forms,including, for example, a capsule, an IV bag, a tablet, a single pump onan aerosol inhaler, or a vial. The quantity of active ingredient (e.g.,a formulation of the disclosed compound or salts thereof) in a unit doseof composition is an effective amount and is varied according to theparticular treatment involved. One skilled in the art will appreciatethat it is sometimes necessary to make routine variations to the dosagedepending on the age and condition of the patient. The dosage will alsodepend on the route of administration. A variety of routes arecontemplated, including oral, pulmonary, rectal, parenteral,transdermal, subcutaneous, intravenous, intramuscular, intraperitoneal,intranasal, and the like. Dosage forms for the topical or transdermaladministration of a compound of this invention include powders, sprays,ointments, pastes, creams, lotions, gels, solutions, patches andinhalants. In a preferred embodiment, the active compound is mixed understerile conditions with a pharmaceutically acceptable carrier, and withany preservatives, buffers, or propellants that are required.

The term “flash dose” refers to compound formulations that are rapidlydispersing dosage forms.

The term “immediate release” is defined as a release of compound from adosage form in a relatively brief period of time, generally up to about60 minutes. The term “modified release” is defined to include delayedrelease, extended release, and pulsed release. The term “pulsed release”is defined as a series of releases of drug from a dosage form. The term“sustained release” or “extended release” is defined as continuousrelease of a compound from a dosage form over a prolonged period.

The phrase “pharmaceutically acceptable” is art-recognized. In certainembodiments, the term includes compositions, polymers and othermaterials and/or dosage forms which are, within the scope of soundmedical judgment, suitable for use in contact with the tissues of humanbeings and animals without excessive toxicity, irritation, allergicresponse, or other problem or complication, commensurate with areasonable benefit/risk ratio.

The phrase “pharmaceutically acceptable carrier” is art-recognized, andincludes, for example, pharmaceutically acceptable materials,compositions or vehicles, such as a liquid or solid filler, diluent,excipient, solvent or encapsulating material, involved in carrying ortransporting any subject composition from one organ, or portion of thebody, to another organ, or portion of the body. Each carrier must be“acceptable” in the sense of being compatible with the other ingredientsof a subject composition and not injurious to the patient. In certainembodiments, a pharmaceutically acceptable carrier is non-pyrogenic.Some examples of materials which may serve as pharmaceuticallyacceptable carriers include: (1) sugars, such as lactose, glucose andsucrose; (2) starches, such as corn starch and potato starch; (3)cellulose, and its derivatives, such as sodium carboxymethyl cellulose,ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5)malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter andsuppository waxes; (9) oils, such as peanut oil, cottonseed oil,sunflower oil, sesame oil, olive oil, corn oil and soybean oil; (10)glycols, such as propylene glycol; (11) polyols, such as glycerin,sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyloleate and ethyl laurate; (13) agar; (14) buffering agents, such asmagnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16)pyrogen-free water; (17) isotonic saline; (18) Ringer's solution; (19)ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxiccompatible substances employed in pharmaceutical formulations.

The compounds of the invention are capable of further forming salts. Allof these forms are also contemplated within the scope of the claimedinvention.

“Pharmaceutically acceptable salt” of a compound means a salt that ispharmaceutically acceptable and that possesses the desiredpharmacological activity of the parent compound.

For example, the salt can be an acid addition salt. One embodiment of anacid addition salt is a hydrochloride salt

The pharmaceutically acceptable salts of the present invention can besynthesized from a parent compound that contains a basic or acidicmoiety by conventional chemical methods. Generally, such salts can beprepared by reacting the free acid or base forms of these compounds witha stoichiometric amount of the appropriate base or acid in water or inan organic solvent, or in a mixture of the two; generally, non-aqueousmedia like ether, ethyl acetate, ethanol, isopropanol, or acetonitrileare preferred. Lists of suitable salts are found in Remington'sPharmaceutical Sciences, 18th ed. (Mack Publishing Company, 1990). Forexample, salts can include, but are not limited to, the hydrochlorideand acetate salts of the aliphatic amine-containing, hydroxylamine-containing, and imine-containing compounds of the presentinvention.

It should be understood that all references to pharmaceuticallyacceptable salts include solvent addition forms (solvates) or crystalforms (polymorphs) as defined herein, of the same salt.

The compounds of the present invention can also be prepared as esters,for example pharmaceutically acceptable esters. For example a carboxylicacid function group in a compound can be converted to its correspondingester, e.g., a methyl, ethyl, or other ester. Also, an alcohol group ina compound can be converted to its corresponding ester, e.g., anacetate, propionate, or other ester.

The compounds of the present invention can also be prepared as prodrugs,for example pharmaceutically acceptable prodrugs. The terms “pro-drug”and “prodrug” are used interchangeably herein and refer to any compoundwhich releases an active parent drug in vivo. Since prodrugs are knownto enhance numerous desirable qualities of pharmaceuticals (e.g.,solubility, bioavailability, manufacturing, etc.) the compounds of thepresent invention can be delivered in prodrug form. Thus, the presentinvention is intended to cover prodrugs of the presently claimedcompounds, methods of delivering the same and compositions containingthe same. “Prodrugs” are intended to include any covalently bondedcarriers that release an active parent drug of the present invention invivo when such prodrug is administered to a subject. Prodrugs thepresent invention are prepared by modifying functional groups present inthe compound in such a way that the modifications are cleaved, either inroutine manipulation or in vivo, to the parent compound. Prodrugsinclude compounds of the present invention wherein a hydroxy, amino,sulfhydryl, carboxy, or carbonyl group is bonded to any group that, maybe cleaved in vivo to form a free hydroxyl, free amino, free sulfhydryl,free carboxy or free carbonyl group, respectively.

Examples of prodrugs include, but are not limited to, esters (e.g.,acetate, dialkylaminoacetates, formates, phosphates, sulfates, andbenzoate derivatives) and carbamates (e.g., N,N-dimethylaminocarbonyl)of hydroxy functional groups, ester groups (e.g., ethyl esters,morpholinoethanol esters) of carboxyl functional groups, N-acylderivatives (e.g., N-acetyl) N-Mannich bases, Schiff bases andenaminones of amino functional groups, oximes, acetals, ketals and enolesters of ketone and aldehyde functional groups in compounds of FormulaI, and the like. See Bundegaard, H. “Design of Prodrugs” p1-92,Elsevier, New York-Oxford (1985).

“Protecting group” refers to a grouping of atoms that when attached to areactive group in a molecule masks, reduces or prevents that reactivity.Examples of protecting groups can be found in Green and Wuts, ProtectiveGroups in Organic Chemistry (Wiley, 2^(nd) ed. 1991); Harrison andHarrison et al., Compendium of Synthetic Organic Methods, Vols. 1-8(John Wiley and Sons, 1971-1996); and Kocienski, Protecting Groups,(Verlag, 3^(rd) ed. 2003).

The term “amine protecting group” is intended to mean a functional groupthat converts an amine, amide, or other nitrogen-containing moiety intoa different chemical group that is substantially inert to the conditionsof a particular chemical reaction. Amine protecting groups arepreferably removed easily and selectively in good yield under conditionsthat do not affect other functional groups of the molecule. Examples ofamine protecting groups include, but are not limited to, formyl, acetyl,benzyl, t-butyldimethylsilyl, t-butdyldiphenylsilyl, t-butyloxycarbonyl(Boc), p-methoxybenzyl, methoxymethyl, tosyl, trifluoroacetyl,trimethylsilyl (TMS), fluorenyl-methyloxycarbonyl,2-trimethylsilyl-ethyoxycarbonyl, 1-methyl-1-(4-biphenylyl)ethoxycarbonyl, allyloxycarbonyl, benzyloxycarbonyl (CBZ),2-trimethylsilyl-ethanesulfonyl (SES), trityl and substituted tritylgroups, 9-fluorenylmethyloxycarbonyl (FMOC), nitro-veratryloxycarbonyl(NVOC), and the like. Other suitable amine protecting groups arestraightforwardly identified by those of skill in the art.

Representative hydroxy protecting groups include those where the hydroxygroup is either acylated or alkylated such as benzyl, and trityl ethersas well as alkyl ethers, tetrahydropyranyl ethers, trialkylsilyl ethersand allyl ethers.

The term “pharmaceutically acceptable salts” is art-recognized, andincludes relatively non-toxic, inorganic and organic acid addition saltsof compositions, including without limitation, therapeutic agents,excipients, other materials and the like. Examples of pharmaceuticallyacceptable salts include those derived from mineral acids, such ashydrochloric acid and sulfuric acid, and those derived from organicacids, such as ethanesulfonic acid, benzenesulfonic acid,p-toluenesulfonic acid, and the like. Examples of suitable inorganicbases for the formation of salts include the hydroxides, carbonates, andbicarbonates of ammonia, sodium, lithium, potassium, calcium, magnesium,aluminum, zinc and the like. Salts may also be formed with suitableorganic bases, including those that are non-toxic and strong enough toform such salts. For purposes of illustration, the class of such organicbases may include mono-, di-, and trialkylamines, such as methylamine,dimethylamine, and triethylamine; mono-, di- or trihydroxyalkylaminessuch as mono-, di-, and triethanolamine; amino acids, such as arginineand lysine; guanidine; N-methylglucosamine; N-methylglucamine;L-glutamine; N-methylpiperazine; morpholine; ethylenediamine;N-benzylphenethylamine; (trihydroxymethyl)aminoethane; and the like.See, for example, J. Pharm. Sci. 66:1-19 T1977.

A “patient,” “subject,” or “host” to be treated by the subject methodmay mean either a human or non-human animal, such as primates, mammals,and vertebrates.

The term “prophylactic or therapeutic” treatment is art-recognized andincludes administration to the host of one or more of the subjectcompositions. If it is administered prior to clinical manifestation ofthe unwanted condition (e.g., disease or other unwanted state of thehost animal) then the treatment is prophylactic, i.e., it protects thehost against developing the unwanted condition, whereas if it isadministered after manifestation of the unwanted condition, thetreatment is therapeutic (i.e., it is intended to diminish, ameliorate,or stabilize the existing unwanted condition or side effects thereof).

The terms “therapeutic agent”, “drug”, “medicament” and “bioactivesubstance” are art-recognized and include molecules and other agentsthat are biologically, physiologically, or pharmacologically activesubstances that act locally or systemically in a patient or subject totreat a disease or condition, such as macular degeneration or otherforms of retinal disease whose etiology involves the accumulation of A2Eand/or lipofuscin. The terms include without limitation pharmaceuticallyacceptable salts thereof and prodrugs. Such agents may be acidic, basic,or salts; they may be neutral molecules, polar molecules, or molecularcomplexes capable of hydrogen bonding; they may be prodrugs in the formof ethers, esters, amides and the like that are biologically activatedwhen administered into a patient or subject.

The phrase “therapeutically effective amount” is an art-recognized term.In certain embodiments, the term refers to an amount of a therapeuticagent that, when incorporated into a polymer, produces some desiredeffect at a reasonable benefit/risk ratio applicable to any medicaltreatment. In certain embodiments, the term refers to that amountnecessary or sufficient to eliminate, reduce or maintain (e.g., preventthe spread of) a tumor or other target of a particular therapeuticregimen. The effective amount may vary depending on such factors as thedisease or condition being treated, the particular targeted constructsbeing administered, the size of the subject or the severity of thedisease or condition. One of ordinary skill in the art may empiricallydetermine the effective amount of a particular compound withoutnecessitating undue experimentation. In certain embodiments, atherapeutically effective amount of a therapeutic agent for in vivo usewill likely depend on a number of factors, including: the rate ofrelease of an agent from a polymer matrix, which will depend in part onthe chemical and physical characteristics of the polymer; the identityof the agent; the mode and method of administration; and any othermaterials incorporated in the polymer matrix in addition to the agent.

The term “ED50” is art-recognized. In certain embodiments, ED50 meansthe dose of a drug which produces 50% of its maximum response or effect,or alternatively, the dose which produces a pre-determined response in50% of test subjects or preparations. The term “LD50” is art-recognized.In certain embodiments, LD₅₀ means the dose of a drug which is lethal in50% of test subjects. The term “therapeutic index” is an art-recognizedterm which refers to the therapeutic index of a drug, defined asLD₅₀/ED₅₀.

The term “substituted,” as used herein, means that any one or morehydrogens on the designated atom is replaced with a selection from theindicated group, provided that the designated atom's normal valency isnot exceeded, and that the substitution results in a stable compound.When the substituent is keto (i.e., ═O), then 2 hydrogens on the atomare replaced. Ring double bonds, as used herein, are double bonds thatare formed between two adjacent ring atoms (e.g., C═C, C═N, or N═N).

With respect to any chemical compounds, the present invention isintended to include all isotopes of atoms occurring in the presentcompounds. Isotopes include those atoms having the same atomic numberbut different mass numbers. By way of general example and withoutlimitation, isotopes of hydrogen include tritium and deuterium, andisotopes of carbon include C-13 and C-14.

The chemical compounds described herein can have asymmetric centers.Compounds of the present invention containing an asymmetricallysubstituted atom can be isolated in optically active or racemic forms.It is well known in the art how to prepare optically active forms, suchas by resolution of racemic forms or by synthesis from optically activestarting materials. Many geometric isomers of olefins, C═N double bonds,and the like can also be present in the compounds described herein, andall such stable isomers are contemplated in the present invention. Cisand trans geometric isomers of the compounds of the present inventionare described and can be isolated as a mixture of isomers or asseparated isomeric forms. All chiral, diastereomeric, racemic, andgeometric isomeric forms of a structure are intended, unless thespecific stereochemistry or isomeric form is specifically indicated. Allprocesses used to prepare compounds of the present invention andintermediates made therein are, where appropriate, considered to be partof the present invention. All tautomers of shown or described compoundsare also, where appropriate, considered to be part of the presentinvention.

When a bond to a substituent is shown to cross a bond connecting twoatoms in a ring, then such substituent can be bonded to any atom in thering. When a substituent is listed without indicating the atom via whichsuch substituent is bonded to the rest of the compound of a givenformula, then such substituent can be bonded via any atom in suchsubstituent. Combinations of substituents and/or variables arepermissible, but only if such combinations result in stable compounds.

When an atom or a chemical moiety is followed by a subscripted numericrange (e.g., C₁₋₆), the invention is meant to encompass each numberwithin the range as well as all intermediate ranges. For example, “C₁₋₆alkyl” is meant to include alkyl groups with 1, 2, 3, 4, 5, 6, 1-6, 1-5,1-4, 1-3, 1-2, 2-6, 2-5, 2-4, 2-3, 3-6, 3-5, 3-4, 4-6, 4-5, and 5-6carbons.

As used herein, “alkyl” is intended to include both branched (e.g.,isopropyl, tert-butyl, isobutyl), straight-chain e.g., methyl, ethyl,propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl), andcycloalkyl (e.g., alicyclic) groups (e.g., cyclopropyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl), alkyl substituted cycloalkylgroups, and cycloalkyl substituted alkyl groups. Such aliphatichydrocarbon groups have a specified number of carbon atoms. For example,C₁₋₆ alkyl is intended to include C₁, C₂, C₃, C₄, C₅, and C₆ alkylgroups. As used herein, “lower alkyl” refers to alkyl groups having from1 to 6 carbon atoms in the backbone of the carbon chain. “Alkyl” furtherincludes alkyl groups that have oxygen, nitrogen, sulfur or phosphorousatoms replacing one or more hydrocarbon backbone carbon atoms. Incertain embodiments, a straight chain or branched chain alkyl has six orfewer carbon atoms in its backbone (e.g., C₁-C₆ for straight chain,C₃-C₆ for branched chain), for example four or fewer. Likewise, certaincycloalkyls have from three to eight carbon atoms in their ringstructure, such as five or six carbons in the ring structure.

The term “substituted alkyls” refers to alkyl moieties havingsubstituents replacing a hydrogen on one or more carbons of thehydrocarbon backbone. Such substituents can include, for example, alkyl,alkenyl, alkynyl, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl,arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl,dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate,phosphonato, phosphinato, cyano, amino (including alkylamino,dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino(including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido),amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromaticor heteroaromatic moiety. Cycloalkyls can be further substituted, e.g.,with the substituents described above. An “alkylaryl” or an “aralkyl”moiety is an alkyl substituted with an aryl (e.g., phenylmethyl(benzyl)).

As used herein, “alkenyl” is intended to include hydrocarbon chains ofeither straight or branched configuration having one or morecarbon-carbon double bonds occurring at any stable point along thechain. For example, C₂₋₆ alkenyl is intended to include C₂, C₃, C₄, C₅,and C₆ alkenyl groups. Examples of alkenyl include, but are not limitedto, ethenyl and propenyl.

As used herein, “alkynyl” is intended to include hydrocarbon chains ofeither straight or branched configuration having one or morecarbon-carbon triple bonds occurring at any stable point along thechain. For example, C₂₋₆ alkynyl is intended to include C₂, C₃, C₄, C₅,and C₆ alkynyl groups. Examples of alkynyl include, but are not limitedto, ethynyl and propynyl.

Furthermore, “alkyl”, “alkenyl”, and “alkynyl” are intended to includemoieties which are diradicals, i.e., having two points of attachment. Anonlimiting example of such an alkyl moiety that is a diradical is—CH₂CH₂—, i.e., a C₂ alkyl group that is covalently bonded via eachterminal carbon atom to the remainder of the molecule.

“Aryl” includes groups with aromaticity, including 5- and 6-membered“unconjugated”, or single-ring, aromatic groups that may include fromzero to four heteroatoms, as well as “conjugated”, or multicyclic,systems with at least one aromatic ring. Examples of aryl groups includebenzene, phenyl, pyrrole, furan, thiophene, thiazole, isothiazole,imidazole, triazole, tetrazole, pyrazole, oxazole, isooxazole, pyridine,pyrazine, pyridazine, and pyrimidine, and the like. Furthermore, theterm “aryl” includes multicyclic aryl groups, e.g., tricyclic, bicyclic,e.g., naphthalene, benzoxazole, benzodioxazole, benzothiazole,benzoimidazole, benzothiophene, methylenedioxyphenyl, quinoline,isoquinoline, napthridine, indole, benzofuran, purine, benzofuran,deazapurine, or indolizine. Those aryl groups having heteroatoms in thering structure may also be referred to as “aryl heterocycles”,“heterocycles,” “heteroaryls” or “heteroaromatics”. The aromatic ringcan be substituted at one or more ring positions with such substituentsas described above, as for example, halogen, hydroxyl, alkoxy,alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy,aryloxycarbonyloxy, carboxylate, alkylcarbonyl, alkylaminocarbonyl,aralkylaminocarbonyl, alkenylaminocarbonyl, alkylcarbonyl, arylcarbonyl,aralkylcarbonyl, alkenylcarbonyl, alkoxycarbonyl, aminocarbonyl,alkylthiocarbonyl, phosphate, phosphonato, phosphinato, cyano, amino(including alkylamino, dialkylamino, arylamino, diarylamino, andalkylarylamino), acylamino (including alkylcarbonylamino,arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl,alkylthio, arylthio, thiocarboxylate, sulfates, alkylsulfinyl,sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido,heterocyclyl, alkylaryl, or an aromatic or heteroaromatic moiety. Arylgroups can also be fused or bridged with alicyclic or heterocyclicrings, which are not aromatic so as to form a multicyclic system (e.g.,tetralin, methylenedioxyphenyl).

The terms “heterocyclyl” or “heterocyclic group” include closed ringstructures, e.g., 3- to 10-, or 4- to 7-membered rings, which includeone or more heteroatoms. “Heteroatom” includes atoms of any elementother than carbon or hydrogen. Examples of heteroatoms include nitrogen,oxygen, sulfur and phosphorus.

Heterocyclyl groups can be saturated or unsaturated and includepyrrolidine, oxolane, thiolane, piperidine, piperazine, morpholine,lactones, lactams such as azetidinones and pyrrolidinones, sultams, andsultones. Heterocyclic groups such as pyrrole and furan can havearomatic character. They include fused ring structures such as quinolineand isoquinoline. Other examples of heterocyclic groups include pyridineand purine. The heterocyclic ring can be substituted at one or morepositions with such substituents as described above, as for example,halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy,aryloxycarbonyloxy, carboxylate, alkylcarbonyl, alkoxycarbonyl,aminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato,phosphinato, cyano, amino (including alkyl amino, dialkylamino,arylamino, diarylamino, and alkylarylamino), acylamino (includingalkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino,imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates,sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido,heterocyclyl, or an aromatic or heteroaromatic moiety. Heterocyclicgroups can also be substituted at one or more constituent atoms with,for example, a lower alkyl, a lower alkenyl, a lower alkoxy, a loweralkylthio, a lower alkylamino, a lower alkylcarboxyl, a nitro, ahydroxyl, —CF₃, or —CN, or the like.

As used herein, “halo” or “halogen” refers to fluoro, chloro, bromo, andiodo. “Counterion” is used to represent a small, negatively chargedspecies such as fluoride, chloride, bromide, iodide, hydroxide, acetate,and sulfate.

“Stable compound” and “stable structure” are meant to indicate acompound that is sufficiently robust to survive isolation, and asappropriate, purification from a reaction mixture, and formulation intoan efficacious therapeutic agent.

“Free compound” is used herein to describe a compound in the unboundstate.

“Extinction coefficient” is a constant used in the Beer-Lambert Lawwhich relates the concentration of the substance being measured (inmoles) to the absorbance of the substance in solution (how well thesubstance in solution blocks light beamed through it from getting out onthe other side). It is an indicator of how much light a compound absorbsat a particular wavelength.

In the specification, the singular forms also include the plural, unlessthe context clearly dictates otherwise. Unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which thisinvention belongs. In the case of conflict, the present specificationwill control.

Throughout the description, where compositions are described as having,including, or comprising specific components, it is contemplated thatcompositions also consist essentially of, or consist of, the recitedcomponents. Similarly, where methods or processes are described ashaving, including, or comprising specific process steps, the processesalso consist essentially of, or consist of, the recited processingsteps. Further, it should be understood that the order of steps or orderfor performing certain actions is immaterial so long as the inventionremains operable. Moreover, two or more steps or actions can beconducted simultaneously.

“Small molecule” is an art-recognized term. In certain embodiments, thisterm refers to a molecule which has a molecular weight of less thanabout 2000 amu, or less than about 1000 amu, and even less than about500 amu.

All percentages and ratios used herein, unless otherwise indicated, areby weight.

The “retina” is a region of the central nervous system withapproximately 150 million neurons. It is located at the back of the eyewhere it rests upon a specialized epithelial tissue called retinalpigment epithelium or RPE. The retina initiates the first stage ofvisual processing by transducing visual stimuli in specialized neuronscalled “photoreceptors”. Their synaptic outputs are processed byelaborate neural networks in the retina and then transmitted to thebrain. The retina has evolved two specialized classes of photoreceptorsto operate under a wide range of light conditions. “Rod” photoreceptorstransduce visual images under low light conditions and mediateachromatic vision. “Cone” photoreceptors transduce visual images in dimto bright light conditions and mediate both color vision and high acuityvision.

Every photoreceptor is compartmentalized into two regions called the“outer” and “inner” segment. The inner segment is the neuronal cell bodycontaining the cell nucleus. The inner segment survives for a lifetimein the absence of retinal disease. The outer segment is the region wherethe light sensitive visual pigment molecules are concentrated in a densearray of stacked membrane structures. Part of the outer segment isroutinely shed and regrown in a diurnal process called outer segmentrenewal. Shed outer segments are ingested and metabolized by RPE cells.

The “macula” is the central region of the retina which contains thefovea where visual images are processed by long slender cones in highspatial detail (“visual acuity”). “Macular degeneration” is a form ofretinal neurodegeneration which attacks the macula and destroys highacuity vision in the center of the visual field. AMD begins in a “dryform” characterized by residual lysosomal granules called lipofuscin inRPE cells, and by extracellular deposits called “drusen”. Drusen containcellular waste products excreted by RPE cells. “Lipofuscin” and drusencan be detected clinically by ophthalmologists and quantified usingfluorescence techniques. They can be the first clinical signs of maculardegeneration.

Lipfuscin contains aggregations of A2E. Lipofuscin accumulates in RPEcells and poisons them by multiple known mechanisms. As RPE cells becomepoisoned, their biochemical activities decline and photoreceptors beginto degenerate. Extracellular drusen may further compromise RPE cells byinterfering with their supply of vascular nutrients. Drusen also triggerinflammatory processes, which leads to choroidal neovascular invasionsof the macula in one patient in ten who progresses to wet form AMD. Boththe dry form and wet form progress to blindness.

“ERG” is an acronym for electroretinogram, which is the measurement ofthe electric field potential emitted by retinal neurons during theirresponse to an experimentally defined light stimulus. ERG is anon-invasive measurement which can be performed on either livingsubjects (human or animal) or a hemisected eye in solution that has beenremoved surgically from a living animal.

As used herein, the term “RAL” means retinaldehyde. The term “RAL-trap”means a therapeutic compound that binds free RAL and thereby preventsthe RAL from Schiff base condensation with membranephosphatidylethanolamine (PE). “Free RAL” is defined as RAL that is notbound to a visual cycle protein. The terms “trans-RAL” and“all-trans-RAL” are used interchangeably and mean all transretinaldehyde.

A2E is a reaction by-product of a complex biochemical pathway called the“visual cycle” which operates collaboratively in both RPE cells andphotoreceptor outer segments. The visual cycle recycles a photoreactivealdehyde chromophore called “retinaldehyde” which is derived fromvitamin A and is essential for vision. In simplified terms, the visualcycle has four principal steps: 1) It converts vitamin A in the RPE intoan aldehyde chromophore with one photoreactive strained double bond(11-cis-RAL); 2) It transports 11-cis-RAL to the retina where the itbinds to a specialized photoreceptor protein called opsin; 3) Lightphotoisomerizes bound 11-cis-RAL to trans-RAL, which initiates therelease of bound RAL from the opsin binding site; 4) It convertstrans-RAL (an aldehyde) to vitamin A (an alcohol) and transports vitaminA back to the RPE where the cycle begins again. The pathway isillustrated in FIG. 1 which shows RPE cells on top and photoreceptorouter segments below (labeled “OS”).

The aldehyde group of RAL helps bind the molecule to opsin by forming areversible chemical bond to an amino acid sidechain in the opsin bindingsite. While the aldehyde group on RAL is essential for anchoring themolecule to the opsin binding site, it is otherwise hazardous because ofits propensity to form Schiff bases with other biological amines. Thereaction cascade for A2E formation is shown in FIG. 2. The first threereactions take place in photoreceptor outer segments and produce anintermediary product called A2PE. Once formed, A2PE partitions intolipid phase and accumulates in photoreceptor outer segment membranes.When RPE cells ingest discarded outer segments, their accumulated A2PEis routed to their lysosomes. The final reaction of FIG. 2 takes placeinside RPE lysosomes and completes the formation of A2E.

As described above, macular degeneration and other forms of retinaldisease whose etiology involves the accumulation of A2E and/orlipofuscin may be treated or prevented by lowering the amount of A2Eformed. Compounds useful for doing so include RAL-traps. RAL-traps lowerthe amount of A2E formed, for example by forming a covalent bond withRAL that has escaped sequestering. RAL that has reacted with an RAL-trapcompound is thereby unavailable to react with phosphatidyl ethanolamine.

Without wishing to be bound by theory, it is thought that treatment of apatient having AMD with an RAL-trap compound will reduce the rate of A2Eformation without rate limiting the visual cycle, thereby avoiding thevisual deficit of night blindness. In contrast, therapeutic agents forAMD treatment that reduce A2E synthesis are thought to rate-limit thevisual cycle by competitive inhibition of retinoid binding sites ofvisual cycle proteins, whereby reduction in the turn-over rate of thevisual cycle, causes a reduction in the formation rate of A2E. Thepresent invention reduces A2E accumulation without competitiveinhibition of retinoid binding sites on visual cycle proteins which isknown to cause night blindness.

In certain embodiments, an RAL-trap is a compound known to form areversible Schiff base adduct with RAL (FIG. 3).

RAL-traps of the invention include cyclic amines as well as 5- and6-membered cyclic- and heterocyclic amines which may have one or morepairs of conjugated double bonds. In one example, the cyclic amines arearomatic.

Such compounds include, for example, aromatic amines, such asbenzocaine:

Useful controls for testing the effectiveness of RAL-traps arelidocaine, a local anesthetic that does not form a Schiff base, thusacting as a negative control; and darkness which slows or shuts down thevisual cycle, as a positive control.

In one embodiment, the RAL-trap compound reacts with free RAL in atwo-step fashion to form a stabilized adduct. For example, RAL and aprimary amine of an RAL-trap compound condense to form a Schiff baseadduct, and an internal cyclization reaction forms an uncharged ringwhich contains the amine nitrogen. This ring formation serves tostabilize the RAL adduct by making dissociation more unfavorableenergetically. This prevents free RAL (i.e., RAL not bound to opsins orother proteins in the visual cycle) from being available to form Schiffbase condensation products with phosphatidylethanolamine and thenceprevents A2E formation. Further, once the ring closes, it prevents theamine nitrogen, now part of the ring, from condensing with a second RALmolecule. Reaction of the RAL-trap with a second RAL molecule is thoughtto be unfavorable, as such reaction would result in formation of anadduct having a structure similar to A2E, having dual RAL groups, withspayed tails which could cause lipid packing problems in biologicalmembranes and therefore membrane detergency. Further, a reaction of theamine nitrogen with a second RAL would cause the nitrogen to becomecharged, which could cause unfavorable activity, including toxicity,such as poisoning the lysosomal proton pump in RPE cells.

Compounds useful as RAL-traps include those according to formula IV:

where X is O, N, N(H), or S, het is an optionally substituted 5 or6-membered heterocycle, n is 0, 1, 2, or 3, and each D is an unbranchedlower alkyl group. Each D can be the same or different.

U is a substituent selected from halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl, lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms.

In one embodiment, each D is methyl.

In one embodiment, the ring substituent(s) (U) is chosen such that thepK_(a) of the first ring NH₂ is approximately 3.5. Examples include thefollowing ring systems with the pK_(a) in parentheses:

In one embodiment, such compounds react with RAL according to themechanism depicted in Scheme 1:

Compounds of formula IV

can be synthesized from the corresponding ester:

A depiction of the reaction between the compound

and RAL is presented in Scheme 2:

Compounds of the invention include RAL-traps having a 5- or 6-memberring. For example, the compounds of the invention preserve theabsorption properties of 11-cis-RAL when the two compounds form a Schiffbase adduct, i.e., that forming the adduct will not increase theextinction coefficient above that of free 11-cis-RAL nor shift its peakabsorbance to a longer wavelength. Without being bound by theory, it isthought that this preservation of absorption properties will minimizetreatment side effects on vision by protecting 11-cis-RAL fromphotoisomerization in the adduct state thereby preserving itschromophore activity should it subsequently dissociate from the adductand re-enter the visual cycle where it will be available to bind toopsin in its photoactive state.

In certain embodiments, the RAL-trap of the invention is a compoundhaving a structure represented by general formula I:

wherein, W, X, Y, and Z are each, independently, N, O, S, CU or CH, suchthat at least one of W, X, Y, and Z is N; n is 0, 1, 2, 3, or 4, A is

D is unbranched lower alkyl, and R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl. Each D canbe the same or different.

Substituents on the alkyl chain of R include a halogen atom; C1-C6 alkyloptionally substituted by a halogen atom, cyano, hydroxyl, carbamoyl,amino, formylamino, lower alkylcarbonylamino, aminosulfonylamino, orlower alkylthio; lower alkylcarbonyl wherein the alkyl portion of loweralkylcarbonyl is optionally substituted by a halogen atom, cyano,hydroxyl, carbamoyl, amino, formylamino, lower alkylcarbonylamino,aminosulfonylamino, or lower alkylthio; carbamoyl; or lower alkylthiowherein the alkyl portion of lower alkylthio is optionally substitutedby a halogen atom, cyano, hydroxyl, carbamoyl, amino, formylamino, loweralkylcarbonylamino, aminosulfonylamino, or lower alkylthio.

U is a substituent selected from halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms.

In one example, U is aryl, for example benzene.

In certain compounds, A is

and D is methyl.

In certain compounds, U is a halo-substituted benzene.

In other compounds, two U substituents on adjacent carbon atoms areattached to form a 5 or 6 membered fused ring. Such rings are optionallysubstituted by groups selected from a halogen atom, hydroxyl, carbamoyl,aryl and amino. In certain compounds two adjacent U substituents canform a benzene. For example, such fused compounds have the structure Ia:

Ia

wherein X, Y, and Z are each, independently, N, O, S, CH, or absent,such that at least one of X, Y, and Z is N; p is 0, 1, 2, or 3, B is ahalogen atom, hydroxyl, carbamoyl, aryl or amino, A is

D is unbranched lower alkyl, and R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl.

Examples of compounds of formula I include pyridine, pyridazine,pyrazine, and pyrimidine compounds.

Pyridazine compounds include:

pyrazine compounds include:

pyrimidine compounds include

Compounds of formula I or Ia include:

In certain embodiments, the RAL-trap of the invention is a compoundhaving a structure represented by general formula II or IIa:

wherein, Q, T, and V are each, independently, N, NH, S, O, CU, or CH,such that at least one of Q, T and V is not CU or CH; the dashed ringrepresents two double bonds within the ring, which comply with thevalency requirements of the atoms and heteroatoms present in the ring, mis 0, 1, or 2, A is

where D is unbranched lower alkyl, R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7 or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl. Forexample, R is C2 alkyl (ethyl).

Substituents on the alkyl chain include a halogen atom; C1-C6 alkyloptionally substituted by a halogen atom, cyano, hydroxyl, carbamoyl,amino, formylamino, lower alkylcarbonylamino, aminosulfonylamino, orlower alkylthio; lower alkylcarbonyl wherein the alkyl portion of loweralkylcarbonyl is optionally substituted by a halogen atom, cyano,hydroxyl, carbamoyl, amino, formylamino, lower alkylcarbonylamino,aminosulfonylamino, or lower alkylthio; carbamoyl; or lower alkylthiowherein the alkyl portion of lower alkylthio is optionally substitutedby a halogen atom, cyano, hydroxyl, carbamoyl, amino, formylamino, loweralkylcarbonylamino, aminosulfonylamino, or lower alkylthio.

U is a substituent selected from a halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms. In oneembodiment, example, U is alkyl. For example, U is methyl, ethyl, orpropyl. In one embodiment, U is a halogen. For example, U is chloro,fluoro, or bromo. In certain compounds, two U substituents on adjacentcarbon atoms are attached to form a 5 or 6 membered fused ring. Suchrings are optionally substituted by groups selected from a halogen atom,hydroxyl, carbamoyl, aryl and amino.

In one example, U is aryl, for example benzene.

In certain compounds, A is

and D is methyl.

In certain compounds, U is a halo-substituted benzene.

Examples include furan and thiophene compounds, such as

In certain embodiments, the RAL-trap of the invention is a compoundhaving a structure represented by general formula III:

wherein, L is a single bond or CH₂; k is 0, 1, 2, 3, or 4; A is

where D is unbranched lower alkyl, R is substituted or unsubstituted C1,C2, C3, C4, C5, C6, C7, or C8, straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7, or C8, branched chain alkyl, k is 0,1, 2, 3, or 4.

Substituents on the alkyl chain include a halogen atom; C1-C6 alkyloptionally substituted by a halogen atom, cyano, hydroxyl, carbamoyl,amino, formylamino, lower alkylcarbonylamino, aminosulfonylamino, orlower alkylthio; lower alkylcarbonyl wherein the alkyl portion of loweralkylcarbonyl is optionally substituted by a halogen atom, cyano,hydroxyl, carbamoyl, amino, formylamino, lower alkylcarbonylamino,aminosulfonylamino, or lower alkylthio; carbamoyl; or lower alkylthiowherein the alkyl portion of lower alkylthio is optionally substitutedby a halogen atom, cyano, hydroxyl, carbamoyl, amino, formylamino, loweralkylcarbonylamino, aminosulfonylamino, or lower alkylthio.

U is a substituent selected from halogen atom; cyano; lower alkylwherein one or more hydrogen atoms on the lower alkyl group areoptionally substituted by groups selected from a halogen atom, hydroxyl,carbamoyl, amino, aryl, and a monocyclic or bicyclic heterocyclic groupcontaining one or more hetero-atoms selected from nitrogen, oxygen, andsulfur atoms; lower alkylthio wherein one or more hydrogen atoms on thealkyl group are optionally substituted by groups selected from a halogenatom, hydroxyl, carbamoyl, amino, and aryl; lower alkylsulfonyl whereinone or more hydrogen atoms on the alkyl group are optionally substitutedby groups selected from a halogen atom, hydroxyl, carbamoyl, amino, andaryl; hydroxyl; lower alkoxy; formyl; lower alkylcarbonyl; arylcarbonyl;carboxyl; lower alkoxycarbonyl; carbamoyl; N-lower alkylcarbamoyl;N,N-di-lower alkylaminocarbonyl; amino; N-lower alkylamino; N,N-di-loweralkylamino; formylamino; lower alkylcarbonylamino; aminosulfonylamino;(N-lower alkylamino)sulfonylamino; (N,N-di-loweralkylamino)sulfonylamino; aryl, optionally substituted by groupsselected from a halogen atom, hydroxyl, carbamoyl, aryl and amino; and amonocyclic or bicyclic heterocyclic group containing one or morehetero-atoms selected from nitrogen, oxygen, and sulfur atoms. Examplesinclude hydroxylamines and alkyl amine compounds.

In certain compounds, A is

and D is methyl.

In certain compounds, U is a halo-substituted benzene.

In other compounds, two U substituents on adjacent carbon atoms areattached to form a 5 or 6 membered fused ring. Such rings are optionallysubstituted by groups selected from a halogen atom, hydroxyl, carbamoyl,aryl and amino. For example, such fused compounds have the structureIIIa:

IIIa

wherein X, Y, and Z are each, independently, N, O, S. CH CB, or absent,such that at least one of X, Y, and Z is N; p is 0, 1, 2, or 3, B is ahalogen atom, hydroxyl, carbamoyl, aryl or amino, A is

D is unbranched lower alkyl, R is substituted or unsubstituted C1, C2,C3, C4, C5, C6, C7, or C8 straight chain alkyl, or substituted orunsubstituted C3, C4, C5, C6, C7 or C8 branched chain alkyl, and L is asingle bond or CH₂.

In some embodiments, two adjacent U substituents form a 6-membered fusedheterocycle, for example, a pyridine ring. In other embodiments, twoadjacent U substituents form 5-membered fused heterocycle. For example,two adjacent U substituents form a thiazole ring. In other embodiments,two adjacent U substituents form an oxazole ring. In other embodiments,two adjacent U substituents form an imidazole ring.

Examples of compounds of formula III or IIIa include:

Reaction of the compound

with RAL produces the following conjugate:

Also included are pharmaceutically acceptable addition salts andcomplexes of the compounds of the formulas given above. In cases whereinthe compounds may have one or more chiral centers, unless specified, thecompounds contemplated herein may be a single stereoisomer or racemicmixtures of stereoisomers. Further included are prodrugs, analogs, andderivatives thereof.

Methods

As discussed above, a disclosed composition may be administered to asubject in order to treat or prevent macular degeneration and otherforms of retinal disease whose etiology involves the accumulation of A2Eand/or lipofuscin. Other diseases, disorders, or conditionscharacterized by the accumulation A2E may be similarly treated.

In one embodiment, a compound is administered to a subject that reducesthe formation of A2E. For example, the compound may compete with PE forreaction with trans RAL, thereby reducing the amount of A2E formed. Inanother embodiment, a compound is administered to a subject thatprevents the accumulation of A2E. For example, the compound competes sosuccessfully with PE for reaction with trans RAL, no A2E is formed.

Individuals to be treated fall into three groups: (1) those who areclinically diagnosed with macular degeneration or other forms of retinaldisease whose etiology involves the accumulation of A2E and/orlipofuscin on the basis of visual deficits (including but not limited todark adaptation, contrast sensitivity and acuity) as determined byvisual examination and/or electroretinography, and/or retinal health asindicated by fundoscopic examination of retinal and RPE tissue fordrusen accumulations, tissue atrophy and/or lipofuscin fluorescence; (2)those who are pre-symptomatic for macular degenerative disease butthought to be at risk based on abnormal results in any or all of thesame measures; and (3) those who are pre-symptomatic but thought to beat risk genetically based on family history of macular degenerativedisease and/or genotyping results showing one or more alleles orpolymorphisms associated with the disease. The compositions areadministered topically or systemically at one or more times per month,week or day. Dosages may be selected to avoid side effects if any onvisual performance in dark adaptation. Treatment is continued for aperiod of at least one, three, six, twelve or more months. Patients maybe tested at one, three, six, twelve months or longer intervals toassess safety and efficacy. Efficacy is measured by examination ofvisual performance and retinal health as described above.

In one embodiment, a subject is diagnosed as having symptoms of maculardegeneration, and then a disclosed compound is administered. In anotherembodiment, a subject may be identified as being at risk for developingmacular degeneration (risk factors include a history of smoking, age,female gender, and family history), and then a disclosed compound isadministered. In another embodiment, a subject may have dry AMD in botheye, and then a disclosed compound is administered. In anotherembodiment, a subject may have wet AMD in one eye but dry AMD in theother eye, and then a disclosed compound is administered. In yet anotherembodiment, a subject may be diagnosed as having Stargardt disease andthen a disclosed compound is administered. In another embodiment, asubject is diagnosed as having symptoms of other forms of retinaldisease whose etiology involves the accumulation of A2E and/orlipofuscin, and then the compound is administered. In another embodimenta subject may be identified as being at risk for developing other formsof retinal disease whose etiology involves the accumulation of A2Eand/or lipofuscin, and then the disclosed compound is administered. Insome embodiments, a compound is administered prophylactically. In someembodiments, a subject has been diagnosed as having the disease beforeretinal damage is apparent. For example, a subject is found to carry agene mutation for ABCA4 and is diagnosed as being at risk for Stargardtdisease before any ophthalmologic signs are manifest, or a subject isfound to have early macular changes indicative of macular degenerationbefore the subject is aware of any effect on vision. In someembodiments, a human subject may know that he or she is in need of themacular generation treatment or prevention.

In some embodiments, a subject may be monitored for the extent ofmacular degeneration. A subject may be monitored in a variety of ways,such as by eye examination, dilated eye examination, fundoscopicexamination, visual acuity test, and/or biopsy. Monitoring can beperformed at a variety of times. For example, a subject may be monitoredafter a compound is administered. The monitoring can occur, for example,one day, one week, two weeks, one month, two months, six months, oneyear, two years, five years, or any other time period after the firstadministration of a compound. A subject can be repeatedly monitored. Insome embodiments, the dose of a compound may be altered in response tomonitoring.

In some embodiments, the disclosed methods may be combined with othermethods for treating or preventing macular degeneration or other formsof retinal disease whose etiology involves the accumulation of A2Eand/or lipofuscin, such as photodynamic therapy. For example, a patientmay be treated with more than one therapy for one or more diseases ordisorders. For example, a patient may have one eye afflicted with dryform AMD, which is treated with a compound of the invention, and theother eye afflicted with wet form AMD which is treated with, e.g.,photodynamic therapy.

In some embodiments, a compound for treating or preventing maculardegeneration or other forms of retinal disease whose etiology involvesthe accumulation of A2E and/or lipofuscin may be administeredchronically. The compound may be administered daily, more than oncedaily, twice a week, three times a week, weekly, biweekly, monthly,bimonthly, semiannually, annually, and/or biannually.

The therapeutics may be administered by a wide variety of routes, asdescribed above. In some embodiments, a compound may be administeredorally, in the form of a tablet, a capsule, a liquid, a paste, and/or apowder. In some embodiments, a compound may be administered locally, asby intraocular injection. In some embodiments, a compound may beadministered systemically in a caged, masked, or otherwise inactive formand activated in the eye (such as by photodynamic therapy). In someembodiments, a compound may be administered in a depot form, sosustained release of the compound is provided over a period of time,such as hours, days, weeks, and/or months. Preferably the compound isadministered topically, as an eye drop formulation. Typical dose rangesinclude 0.5 to 5 mg/100 g for oral formulations and 0.5% to 5% solutionsfor eye drop formulations.

The compounds of the invention are provided in therapeutic compositions.The compound is present in an amount that is therapeutically effective,which varies widely depending largely on the particular compound beingused. The preparation of pharmaceutical or pharmacological compositionswill be known to those of skill in the art in light of the presentdisclosure. Typically, such compositions may be prepared as injectables,either as liquid solutions or suspensions; solid forms suitable forsolution in, or suspension in, liquid prior to injection; as tablets orother solids for oral administration; as time release capsules; or inany other form currently used, including eye drops, creams, lotions,salves, inhalants and the like. Compositions may also be delivered viamicrodevice, microparticle or sponge.

Upon formulation, therapeutics will be administered in a mannercompatible with the dosage formulation, and in such amount as ispharmacologically effective. The formulations are easily administered ina variety of dosage forms, such as the type of injectable solutionsdescribed above, but drug release capsules and the like can also beemployed.

In this context, the quantity of active ingredient and volume ofcomposition to be administered depends on the host animal to be treated.Precise amounts of active compound required for administration depend onthe judgment of the practitioner and are peculiar to each individual.

A minimal volume of a composition required to disperse the activecompounds is typically utilized. Suitable regimes for administration arealso variable, but would be typified by initially administering thecompound and monitoring the results and then giving further controlleddoses at further intervals. The amount of compound incorporated into thecomposition also depends upon the desired release profile, theconcentration of the compound required for a biological effect, and thelength of time that the biologically active substance has to be releasedfor treatment. In certain embodiments, the biologically active substancemay be blended with a polymer matrix at different loading levels, in oneembodiment at room temperature and without the need for an organicsolvent. In other embodiments, the compositions may be formulated asmicrospheres. In some embodiments, the compound may be formulated forsustained release.

For oral administration in the form of a tablet or capsule (e.g., agelatin capsule), the active drug component can be combined with anoral, non-toxic pharmaceutically acceptable inert carrier such asethanol, glycerol, water and the like. Moreover, when desired ornecessary, suitable binders, lubricants, disintegrating agents andcoloring agents can also be incorporated into the mixture. Suitablebinders include starch, magnesium aluminum silicate, starch paste,gelatin, methylcellulose, sodium carboxymethylcellulose and/orpolyvinylpyrrolidone, natural sugars such as glucose or beta-lactose,corn sweeteners, natural and synthetic gums such as acacia, tragacanthor sodium alginate, polyethylene glycol, waxes and the like. Lubricantsused in these dosage forms include sodium oleate, sodium stearate,magnesium stearate, sodium benzoate, sodium acetate, sodium chloride,silica, talcum, stearic acid, its magnesium or calcium salt and/orpolyethyleneglycol and the like. Disintegrators include, withoutlimitation, starch, methyl cellulose, agar, bentonite, xanthan gumstarches, agar, alginic acid or its sodium salt, or effervescentmixtures, and the like. Diluents, include, e.g., lactose, dextrose,sucrose, mannitol, sorbitol, cellulose and/or glycine.

Injectable compositions are preferably aqueous isotonic solutions orsuspensions, and suppositories are advantageously prepared from fattyemulsions or suspensions. The compositions may be sterilized and/orcontain adjuvants, such as preserving, stabilizing, wetting oremulsifying agents, solution promoters, salts for regulating the osmoticpressure and/or buffers. In addition, they may also contain othertherapeutically valuable substances. The compositions are preparedaccording to conventional mixing, granulating or coating methods,respectively, and contain about 0.1 to 75%, preferably about 1 to 50%,of the active ingredient.

The compounds of the invention can also be administered in such oraldosage forms as timed release and sustained release tablets or capsules,pills, powders, granules, elixers, tinctures, suspensions, syrups andemulsions.

The compounds of the invention can also be administered topically, suchas directly to the eye, e.g., as an eye-drop or ophthalmic ointment. Eyedrops typically comprise an effective amount of at least one compound ofthe invention and a carrier capable of being safely applied to an eye.For example, the eye drops are in the form of an isotonic solution, andthe pH of the solution is adjusted so that there is no irritation of theeye. In many instances, the epithelial barrier interferes withpenetration of molecules into the eye. Thus, most currently usedophthalmic drugs are supplemented with some form of penetrationenhancer. These penetration enhancers work by loosening the tightjunctions of the most superior epithelial cells (Burstein, 1985, TransOphthalmol Soc UK 104(Pt 4): 402-9; Ashton et al., 1991, J Pharmacol ExpTher 259(2): 719-24; Green et al., 1971, Am J Ophthalmol 72(5):897-905). The most commonly used penetration enhancer is benzalkoniumchloride (Tang et al., 1994, J Pharm Sci. 83(1): 85-90; Burstein et al.,1980, Invest Ophthalmol Vis Sci. 19(3): 308-13), which also works aspreservative against microbial contamination. It is typically added to afinal concentration of 0.01-0.05%.

Screening Methods

Suitable compounds may be identified by a variety of screening methods.For example, a candidate compound may be administered to a subject thathas or is at risk of developing macular degeneration or other forms ofretinal disease whose etiology involves the accumulation of A2E and/orlipofuscin, and the accumulation of a retinotoxic compound, such as A2E,can be measured. A drug that results in reduced accumulation of aretinotoxic compound compared to a control (absence of the drug) wouldthus be identified as a suitable drug.

Alternatively, RAL and RPE tissue may be analyzed for the presence ofA2E and/or its precursors.

EXAMPLES Example 1: Synthesis of Compounds

The compounds of the invention, and related derivatives, can besynthesized by methods known to one skilled in the art. For example, adetailed method for the synthesis of compound 7 is described below inScheme 3.

A mixture of acetonitrile (60 mL) and ethyl 2-amino-1,3,thiazole-4-carboxilate (0.54 g, 3 mmol) and N-fluorobenzenesulfonimide(3.3 g, 9 mmol) was heated at reflux temperature for 18 hours. The colorchanged from yellow to reddish. The reaction mixture was concentratedand purified using chromatographic methods: column chromatography (2-5%methanol-chloroform), prep-TLC (2% methanol-chloroform), prep HPLC(column: Phenomenex Luna Phenyl-hexyl (150×4.6 mm ID, 3 μm packing),β₁=215 nm, flow rate: 0.8 mL/min, injection volume: 5 mL, run time: 31min, mobile phase gradient: A: water w 0.1% v/v TFA; B MeCN w 0.1% v/vTFA), and prep-TLC (10% meOH-chloroform) to afford a brown solid (380mg). LCMS m/z: 145, 173, 191, 381, and 399. ¹H NMR (300 MHz, CDCl₃)δ:1.3 ppm (m, 3H Me) and 4.8 ppm (m, 2H, CH₂).

Example 2: In Vitro Schiff Base Confirmation

UV/VIS spectroscopy was used to monitor Schiff base condensation of RALwith the primary amine of a compound of the invention. The in vitroanalysis of the Schiff base condensation product with RAL was performedfor the disclosed compounds 1, 2, 3, 4, 5, and 6 and the results areshown in Table 1.

In the solution phase analysis, the λ_(max) value of both the freecompound and the RAL Schiff base condensation product (RAL-SBC) aremeasured along with the value for tau of the RAL-SBC. As used herein,“RAL-SBC” means the Schiff base condensation product of RAL and aRAL-compound. Solution phase analysis is performed using a 100:1 mixtureof compound and RAL using protocols known in the art. Several solventsystems were tested including aqueous, ethanol, octanol, andchloroform:methanol (various, e.g., 2:1). The solution kinetics aremeasured and found to be highly dependent on solvent conditions. FIGS.4a and 4b show the results of Schiff base condensation of compound 6 andRAL (100:1) in chloroform:methanol (2:1).

Solid phase analysis of the Schiff base condensation is also performedusing a 1:1 mixture of compound to RAL. The solid phase analysis isperformed using protocols known in the art. The mixture is dried undernitrogen and condensation reaction occurs to completion.

Lipid phase analysis is performed using protocols known in the art andλ_(max), tau (RAL-SBC vs. APE/A2PE), and competitive inhibition aremeasured. Liposome conditions are closer to in situ conditions.

Example 3: Log P and pKa Values

Log P values are shown in Table 1 for compounds 1, 2, 3, 4, 5, and 6.The partition coefficient (log P) is the log of the ratio[X_(organic)]/[X_(aqueous)] for a compound X at a pH where X at a pHwhere X is neutral, not ionized. Values above zero denote increasinglipophilic properties, and below zero, increasing hydrophilicproperties. Octanol is commonly used as the organic solvent. Examplesare as follows:

Log P=2 X is 10² more soluble in organic solvent than aqueous

Log P=0 X is equally soluble in both

Log P=−2 X is 10² more soluble in aqueous solvent then organic

Log P values are typically calculated algorithmically (not measuredexperimentally) by software programs such as Pallas and ACDlabs.Calculation results vary by software product and are regarded as orderof magnitude approximations.

pKa values are shown in Table 1 for compounds 1, 2, 3, 4, 5, 6, and 7.pKa values are measured using known methods in the art. The acidity of ageneral acid, HA, is expressed by the chemical equation:HA+H₂O

H₃O⁺+A⁻which is described by the equilibrium constant K. According to thegeneral definition of an equilibrium constant, K is expressed as

$K = \frac{\lbrack {H_{3}O^{+}} \rbrack\lbrack A^{-} \rbrack}{\lbrack{HA}\rbrack\lbrack {H_{2}O} \rbrack}$Because, in aqueous solution, [H₂O] will be constant at 55 moles 1⁻¹,that number may be incorporated into a new constant Ka, defined as theacidity constant:

$K_{a} = {\frac{\lbrack {H_{3}O^{+}} \rbrack\lbrack A^{-} \rbrack}{\lbrack{HA}\rbrack}\mspace{14mu}{moles}\mspace{14mu} 1^{- 1}}$This measurement when put in logarithmic scale is pKa=−log Ka. An acidwith a pKa lower than 1 is defined as strong, one with a pKa higher than4 is weak. The volume of distribution (V) of a drug may widely varydepending on the pKa of the compound. The volume of distribution relatesto the amount of compound in the body to the concentration of compoundin the blood or plasma.

TABLE 1 free RAL-SBC calculated λmax λmin tau logP logP pKa pKa IDStructure nm nm sec vendor Pallas NH₂ ring N 1

284 333 10,000 1.2 1.0 — 3.0 2

294 340 3,000 1.3 0.5 — 2.1 3

256 330 10,000 0.8 0.2 — 5.4 4

260 325 10,000 1.4 0.9 — 4.5 5

335 336 3,000 2.3 1.4 3.66 n.a. 6

319 541 50 1.8 1.7 3.51 n.a. 7

— — — n.a. 1.2 — 2.7

Example 4: ERG Analysis of Dark Adaptation

Dark adaptation is the recovery of visual sensitivity following exposureto light. Dark adaptation has multiple components including both fast(neuronal) processes and slow (photochemical) process. Regeneration ofvisual pigment is related to the slow photochemical process. Darkadaptation rates are measured for several reasons. Night blindnessresults from a failure to dark adapt (loss of visual light sensitivity).It is possible to find a safe dose for night vision by measuring drugeffects on dark adapted visual light sensitivity.

An electroretinogram (ERG) is used measure dark adaptation under normalvs. drug conditions. ERG is the measurement of the electric fieldpotential emitted by retinal neurons during their response to anexperimentally defined light stimulus. More specifically, ERG measuresretinal field potentials at the cornea after a flash of light (e.g., 50ms). Field strengths are 10² to 10³ microvolts, originating in retinalcells.

ERG is a non-invasive measurement which can be performed on eitherliving subjects (human or animal) or a hemisected eye in solution thathas been removed surgically from a living animal. ERG requires generalanesthesia which slows dark adaptation and must be factored intoexperimental design.

In a typical ERG analysis of dark adaptation experiment, every rat isdark adapted for hours to reach a consistent state of light sensitivity.The rat is then “photo-bleached,” i.e., exposed briefly to light strongenough to transiently deplete the retina of free 11-cis-RAL (e.g., 2 minat 300 lux). The rat is then returned to dark immediately to initiatedark adaptation, i.e., recovery of light sensitivity due to regenerationof visual pigment. ERG is used to measure how quickly the rat adapts todark and recovers light sensitivity. Specifically, a criterion responsevariable is defined for light sensitivity (see FIG. 5).

The ERG measurement is taken after a specific duration of post-bleachdark recovery (e.g., 30 min) determined previously by kinetic analysis(see FIGS. 6a and 6b ). A curve fit is used to calculate value for thesensitivity variable. FIG. 6a shows recovery with anesthesia in the samerat including dark adaptation kinetics for Y₅₀ and σ. Slower adaptationis observed with less light sensitivity where Y₅₀ reaches −4.0 andtau=22.6 min. FIG. 6b shows recovery without anesthesia (5 differentrats) including dark adaptation kinetics for Y₅₀. Faster adaptation isobserved with more light sensitivity where Y₅₀ reaches −5.5 and tau=9.2min.

The same paradigm as described above is followed for dose ranging. Asshown below in FIG. 7, in the ERG dose ranging protocol, compound 6 i.p.lowers light sensitivity of dark adapted rats in a dose dependentmanner. The effect on vision decreases after 3 hours.

Example 5: NMR Analysis of RAL Reactions

NMR spectroscopy was used to monitor Schiff base condensation and ringformation of RAL with the primary amine of a compound of the invention.The NMR analysis of the RAL reactions was performed for the disclosedcompounds 6, 8 and 9 as shown in FIG. 8 and Table 2. Condensation ratesin pure chloroform are as follows: compound 6>8>9.

TABLE 2 Compound tau (minutes) # Structure condense ring 6

3 n.a. 8

122 109 9

320 568

Example 6: Inhibition of A2E Formation

This experiment is designed to establish proof of concept that chronici.p. injection of a RAL-trap compound lowers the accumulation rate ofA2E in wild type Sprague Dawley rats. These experiments compare thetreatment efficacy of RAL-trap compounds to that of control compoundsand lack of treatment.

Materials and Methods:

The study is performed with wild type Sprague Dawley rats. Rat treatmentgroups include for example, 8 rats of mixed gender per treatmentcondition. Each animal is treated with one of the following conditions:

-   -   Controls: (1) 13-cis retinoic acid to inhibit retinoid binding        sites of visual cycle proteins as a protocol control, in that        such treatment reduces the amount of free trans-RAL that is        released and thereby available to form A2E, but with undesirable        side effects of night blindness, and (2) a commercially        available compound known clinically to modulate retinal function        in humans and known experimentally to form a Schiff base adduct        with free RAL, both in vitro and in vivo in animal models.    -   Vehicle    -   Compound    -   Untreated

A number of compounds are tested, e.g., 4 compounds. The compounds aretested across a dose range including 1, 5, 15, and 50 mg/kg. Treatmentis administered daily for 8 weeks by i.p. injection.

Chemistry:

The experiments use a variety of chemistry services. For example, theseexperiments use commercially available compounds with analyticalspecification sheets to characterize the impurities. Compounds are alsosynthesized. Compounds are prepared in quantities sufficient for therequired dosing. Formulations of the compound are suitable for use ininitial animal safety studies involving intraperitoneal (i.p.)injection. The following three attributes of the Schiff base reactionproduct of trans-RAL with compounds of the invention are determined:

-   -   stability with respect to reaction rates    -   absorption properties, specifically uv-vis absorption maxima and        extinction coefficients (see, e.g., FIG. 5 in Rapp and Basinger,        Vision Res. 22:1097, 1982) or NMR spectral analysis of reaction        kinetics    -   log P and log D solubility values e.g. calculated        Biology and Biochemistry:

The experiments described herein use a variety of biology andbiochemistry services. A “no effect level” (NOEL) dose of compounds ofthe invention for daily treatment with an eye drop formation isestablished, e.g., in the rabbit with an ocular irritation protocol andin the rodent with ERG measurement of dark adaptation in visualresponses to light stimulation. After treatment and before eyeenucleation, the following non-invasive assays are performed in animals,e.g., rabbits:

-   -   RPE and photoreceptor cell degeneration, as evident by fundus        photography (Karan, et al., 2005, PNAS 102:4164)    -   Extracellular drusen and intracellular lipofuscin as measured by        fundus fluorescent photography (Karan et al., 2005)

Light responses are characterized by ERG (Weng et al., Cell 98:13,1999). Intracellular A2E concentration of retinal RPE cell extracts ismeasured in all treated animals upon the conclusion of the treatmentprotocol using an analytical method such as those described by Karan etal., 2005; Radu et al., 2003; and Parish et al., PNAS 95:14609, 1998.For example, in a sample of treated animals, one eye is assayed, and theother eye is saved for histology analysis (as described below). In theremaining animals, both eyes are assayed separately for A2E formation.

In the post-treatment eyes set aside for histology (as described above),the morphology of retinal and RPE tissue is assessed with lightmicroscopy histology techniques (Karan et al., 2005, with the exceptionthat electron microscopy is not used in the experiments describedherein).

The safety of the treatment regimen is assessed for example using acombination of:

-   -   Daily documented observation of animal behavior and feeding        habits throughout the treatment period    -   Visual performance as measured by ERG at the end of the        treatment period    -   Ocular histology at the end of the treatment period.

INCORPORATION BY REFERENCE

The entire disclosure of each of the patent documents, includingcertificates of correction, patent application documents, scientificarticles, governmental reports, websites, and other references referredto herein is incorporated by reference in its entirety for all purposes.In case of a conflict in terminology, the present specificationcontrols.

Other Embodiments

While the invention has been described in conjunction with the detaileddescription thereof, the foregoing description is intended to illustrateand not limit the scope of the invention, which is defined by the scopeof the appended claims. Other aspects, advantages, and modifications arewithin the scope of the following claims. It will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the scope of the invention encompassed bythe appended claims.

What is claimed:
 1. A compound selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.
 2. The compound of claim1 which is:

or a pharmaceutically acceptable salt thereof.
 3. The compound of claim1 which is:

or a pharmaceutically acceptable salt thereof.
 4. The compound of claim1 which is:

or a pharmaceutically acceptable salt thereof.
 5. A pharmaceuticalcomposition comprising a compound selected from the group consisting of:

and a pharmaceutically acceptable salt thereof; and a pharmaceuticallyacceptable carrier.
 6. The pharmaceutical composition of claim 5,wherein the compound is:

or a pharmaceutically acceptable salt thereof; and a pharmaceuticallyacceptable carrier.
 7. The pharmaceutical composition of claim 5,wherein the compound is:

or a pharmaceutically acceptable salt thereof; and a pharmaceuticallyacceptable carrier.
 8. The pharmaceutical composition of claim 5,wherein the compound is:

or a pharmaceutically acceptable salt thereof; and a pharmaceuticallyacceptable carrier.